Gatun Dam

The Gatun Dam is a large earthen dam across the Chagres River in Panama, near the town of Gatun. The dam, constructed between 1907 and 1913, is a crucial element of the Panama Canal; it impounds the artificial Gatun Lake, which in turn carries ships for 33 kilometres (21 mi) of their transit across the Isthmus of Panama. In addition, a hydro-electric generating station at the dam generates electricity which is used to operate the locks and other equipment in the canal.

Construction of the dam was a great engineering achievement, eclipsed only by the parallel excavation of the Culebra Cut; at the time of completion, the dam was the largest earth dam in the world, and Lake Gatun was the largest artificial lake in the world.

The dam is situated in the valley of the Chagres River, about 10 kilometres (6.2 mi) from its mouth in the Caribbean Sea. The hills bordering the valley of the Chagres form a gap just over 2 kilometres (1.2 mi) wide at this point, with a natural rocky hill in the centre of the gap. The gap is filled by an earth dam, 640 metres (2,100 ft) thick at the base, 2,300 metres (7,500 ft) long along the top, 121-metre (397 ft) thick at the water level, and 30-metre (98 ft) thick at the top, which is 9 metres (30 ft) above the normal lake level.

The spillway for the dam is constructed on the central hill; it consists of a semi-circular concrete dam, which regulates the flow of water down a concrete channel built into the back slope of the hill. The spillway dam itself measures 225 metres (738 ft) along the top; its crest is at 16 feet (4.9 m) below the normal lake level. The spillway is designed so that water pouring over the semi-circular dam converges at the bottom from opposite directions and neutralises its own force, thus minimising erosion below.

The spillway dam is topped by 14 gates, supported by concrete piers and each 14 metres (46 ft) wide by 6 metres (20 ft) high. These gates, which are electrically operated, are raised or lowered to control the flow of water; with the lake level at 26.5 metres (87 ft), its planned maximum level, the capacity of the spillway is 4,100 cubic metres (140,000 cu ft) per second, more than the maximum flow of the Chagres River. In addition to this, the culverts in the locks can dispose of 1,400 cubic metres (49,000 cu ft) per second.

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